Blender 3D: Noob to Pro/Making Fire

We're going to create a camp fire with a simple particle system. This tutorial is based on the method described in the Blender Manual. The result of this tutorial is shown in Fig. 1, the Blend-File is included at the bottom of this page.

If you need more realistic looking fire, you should use the method described in BlenderArt Magazine No. 16, though that method is more advanced and uses Compositing Nodes heavily.

The starting point of the tutorial is how fire behaves physically. The flames are made of hot gases. These accelerate upwards due to their lower density in contrast to the cooler air in the environment. Flames are in the middle hot and bright, to the outside they are darker.

Life: 16.6 I've adjusted the lifetime of the particles to their speed. Both parameters together regulate the height of the flame.

Rand: 0.5 The lifetime is changed randomly.

Emit from:

Random

Faces

Even

Random

This creates particles with a random distribution on the faces of the emitter object.

Please note, that the particle simulation is only fully calculated if the bake parameters in the Bake panel match the positive lifetime of the particles. If you want to run the simulation longer than 250 frames, you have to increase the End frame in the Bake panel as well. This is independent whether you want to bake or not.

The movement of the particles is controlled with particle physics. You set the Initial Velocity and let the physics do the rest.

Normal: -0.099 The particles are emitted slightly against the direction of the face normal. This leads to a bit wider fire at the base.

Random: 0.014 This creates a random start velocity as well in speed as in direction (you could use a texture to randomize only the speed, see the discussion page for that).

After you have given the particles an initial velocity they are moved by forces.

AccZ: 2.57 A force in positive Z direction (upwards).

As far as I can see AccZ does not exist in later versions(2.69 in my case); the alternative appears to be to set the Physics to Fluid and set a positive Buoyancy (something around 0.75 looks reasonable).

Drag: 0.1 Air drag decelerates the particles.

Brown: 1.99 Random movement simulates agitated air movement.

Figure 2c: Particles without material

The particle system is finished. Until now is doesn't look like much (see the white Blob in Fig. 2c). Therefore the emitter will get a material, this material will be animated.

The particles "pop" into life and vanish suddenly. We should change that. Therefore we're going to animate the Alpha value of the particles.

Make sure the material buttons are visible in the buttons window.

Change to frame 21, move the mouse cursor over the button window and press I->Alpha. This is going to be the maximum visibility of the particles.

Change to frame 1. Change the Alpha value to 0 and insert the next key.

Change to frame 100. Change the Alpha value to 0 again and insert the third key.

If you want to see the IPO curve in the IPO Editor window you must change the IPO Type selector in the window header from Object to Material.

Note: An animation of particle material is mapped from the first 100 frames to the lifetime of the particles. I.e. if the material is faded out during the first 100 frames (the ipo curve is 100 frames long) the particle will be faded out during it's own lifetime, no matter how long that is. This holds true however only for Point visualization of particles, not for object visualization.

The Alpha value therefore changes during the individual lifetime of each particle from 0 to 0.8 and back to 0 (Fig. 3c).

Note: In Blender 2.6, IPO curves no longer exist. Select the graph editor view to get the same capabilities. Also note that in the texture settings from the previous section you need to enable (and set to 1) the Alpha setting in the "influence" section, otherwise the Alpha animation will be applied to the particle system as a whole not to the individual particles.